The present invention relates to a method of reducing the leakage of storm waters from a storm sewer system and, more particularly, it relates to the insertion of a flexible sleeve attached to the perimeter of the storm sewer line in the catch basin at the upstream end of a given segment of storm sewer to prevent or reduce effluent water from the storm sewer from entering into the sanitary sewer system.
Water control in municipal areas is normally divided into two components: sanitary and storm. The lines which collect sanitary waste lead to a facility with special apparatus and methods for removal of those materials which would degrade the quality of the stream accepting the discharge. Storm water, except in very unusual circumstances, may be discharged into adjacent streams without any treatment. The collection systems for these two streams are frequently inadequately isolated from one another. In fact early in the twentieth century they were some times deliberately combined so that storms would flush the sanitary system, resulting in the dumping of raw sewage into streams when the capacity of the treatment plant was exceeded. This became environmentally unacceptable, especially to those immediately downstream. Such systems have now been replaced.
In addition, the drains for storm waters from the downspouts and footers of homes are frequently tied into the sanitary sewer since the sanitary sewer is normally installed lower than the storm sewer. Water from this source contributes to the overload experienced at treatment plants during rainstorms. A concerted effort has been made in most communities to eliminate this source of storm waters entering the sanitary lines. In spite of these extensive and frequently expensive efforts, unacceptable flow increases in the sanitary lines during rain storms or winter runoff is still a common occurrence. This leads to the backup of raw sewage into basements as well as sewage facility overload. Holding ponds are commonly installed to prevent overflow into nearby streams, but this does not prevent raw sewage backup. In fact such backup may occur even in new homes that are connected to an existing system. This occurs because of the general nature of construction. Sanitary sewers have been intended to be hydrostatically sound for a number of years but older installations, constructed of vitreous tile joined with a mastic, commonly leak at these joints.
At the time of installation, the tile typically was laid level and covered with crushed rock. The rock was used to avoid the subsidence which would be encountered with soil fill. Furthermore the rock provided a firm base for the street, however, this structure allows for the rapid passage of water in and around the sanitary sewer line. When a break or any deterioration of the sanitary sewer line occurs, extraneous water outside the sanitary sewer line, such as storm water, finds its way into the sanitary sewer system. Streets are normally crowned to provide drainage. This requires cross street storm connections unless two parallel lines are provided for each street. Such parallel lines are seldom used because of the costs involved. It should further be noted that the object of storm drainage is to remove the water from the streets. Any water that can soak into the ground need not be provided for by larger lines downstream. Hence, no effort was made in older installations to insure the hydraulic integrity of storm lines. The result of this combination is that leaky storm lines frequently pass over crushed rock beds which cover leaky sanitary sewers. The net result is that very large quantities of storm waters are transferred from the storm sewers to the sanitary sewers with all the problems discussed above.
The situation can be corrected by replacement of one or both lines. This, however, is very labor intensive and, because of the great increase in underground utilities, represents an ever increasingly costly approach as well. Removal of any constrictions and construction of holding ponds have also been used. This, of course does not directly address the problem. In fact, new allotments have experienced raw sewage backup because of the inflow of storm water into the sanitary line even though the line immediately in front of the house is hydrostatically sound.
U.S. Pat. Nos. 4,009,063; 4,064,211; and 4,135,958 teach the use of a hollow plastic cylinder which is folded in such a manner that it can be inserted into the existing sanitary sewer. Pressure is applied to force this liner out against the walls. Heat is applied to cure this liner in the expanded shape. Extensive use of this method requires a method of reopening tap-in junctions which are closed off by the new liner. Special machines for this purpose are disclosed in U.S. Pat. Nos. 4,685,983; 4,819,721; and 5,368,423. In addition some digging is required with all the attendant dangers of damaging underground utilities whose positions may not be accurately known. This method had been found particularly cost effective only in instances where a large number of phone, electrical, and other utility lines are known to exist.
Accordingly, there is a need for a convenient and practical means for insuring that storm water is carried away by the storm sewer without leaking into the sanitary sewer system.